APPLICANT'S DESCRIPTION: Although the mortality associated with surgical repair of congenital heart defects has declined, the prevalence of adverse post-operative neurological sequalae, ranging from focal injury to subtle neurobehavioral dysfunctions is elevated among these patients. Some of the brain injury associated with cardiac surgery may be attributable to the procedures used intra-operatively to protect vital organs, particularly cardiopulmonary bypass (CPB). Studies attempting to determine the neurological risks associated with CPB have been hampered by the difficulty of assembling an appropriate control group of comparable patients whose repair procedure does not involve CPB. Recent advances in interventional cardiology have made available patients with congenital heart defects that can be repaired by means of transcatheter closure, without the need for CPB. The potential neurological risks associated with this repair strategy are not yet clear. Data from a retrospective (nonrandomized) pilot study suggested, however, that patients with an atrial septal defect (ASD) repaired by transcatheter closure scored significantly higher than patients with an ASD repaired surgically in terms of Full-Scale IQ, Performance IQ, and visual-spatial skills. The proposed study is a prospective single-center randomized trial involving patients 3 to 15 years 11 months of age presenting for repair of an ASD. Patients will be randomly assigned to two treatment groups, closure by means of standard open-heart surgical methods that involve a period of mildly hypothermic CPB, or by means of a transcatheter delivered device. The target sample size is 20 patients per treatment group, to be enrolled over a 3.5-year period. Each patient will be administered a battery of age-appropriate neurobehavioral tests prior to ASD closure and the same battery of tests 12 months after closure. The primary endpoint is Full-Scale IQ. The hypothesis is that, in intention-to-treat analyses, change in Full-Scale IQ between the baseline and post-closure assessments will differ depending on treatment group, with surgical patients performing significantly worse than device patients. Secondary endpoints to be measured include visual-spatial skills, attention/vigilance, fine motor function, new learning, academic skills, and behavior. Implications for the clinical management of many patients with congenital heart defects will be substantial if the results indicate that even a brief period of CPB is associated with an increased risk of subsequent neurobehavioral dysfunction.